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From: Dan Purgert <dan@djph.net>
Newsgroups: sci.electronics.design
Subject: Re: "Safe" cell phone WiFi capabilities?
Date: Mon, 20 May 2024 17:03:40 -0000 (UTC)
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On 2024-05-20, Don Y wrote:
> On 5/20/2024 4:37 AM, Dan Purgert wrote:
>> On 2024-05-20, Don Y wrote:
>>> On 5/20/2024 4:02 AM, Dan Purgert wrote:
>>>> On 2024-05-17, Don Y wrote:
>>>>> On 5/17/2024 5:55 AM, Dan Purgert wrote:
>>>>>> On 2024-05-17, Don Y wrote:
>>>>>>> For "nominal" cell phones (i.e., taking into consideration
>>>>>>> that not ever subscriber buys The Latest and Greatest),
>>>>>>> what's the "base" WiFi capability one would feel comfortable
>>>>>>> assuming?  ac?  ax?
>>>>>>
>>>>>> Assuming you're limiting the question to the set of cellphones that
>>>>>> actually implement wifi, 802.11b ... but what are you *REALLY*
>>>>>> trying to ask for?
>>>>>
>>>>> There are several different "generations" of WiFi, each with
>>>>> different effective (data) bandwidths.
>>>>> [...]
>>>>
>>>> No. /FLAGSHIP/ models certainly have a high chance of supporting
>>>> 802.11ax, but that doesn't mean "any" phone.
>>>>
>>>> Again, what are you *REALLY* trying to ascertain here?
>>>
>>> But, in practice, most phones support something more capable
>>> than 802.11b -- just like most enets support something more
>>> capable than 10BaseT/2.
>> 
>> It's almost like "the base" isn't what you want then.
>> [...]
>> Which is why you toss in an 802.11ax AP (or 802.11ac, if the ax units
>> are prohibitively expensive for your house/office/whatever), and leave
>> it up to the client device to negotiate for the best common option.
>
> And, when you want to pass a gigabit of data to the phone each second,
> how does that AP help the phone GET the data when the pipe TO THE HANDSET
> is considerably narrower?!

Then I buy a phone that can support 802.11ac Wave2 with 160 MHz channel
width, and at least 3x3 spatial streams. Assuming, of course:

  - that the AP supports those minimum requirements as well, AND
  - The conditions allow for negotiation of MCS8 (~2300 mbps link rate,
    ballpark 1gpbs sustained data rate, but WiFi math is "fun") AND
  - There aren't other devices also requesting airtime (especially ones
    using slower options -- 2x2 streams, 802.11n, MCS5,  etc.) AND
  - The server has enough bandwidth (incl. read buffers, disk I/O, etc.)
    to sustain that 1gpbs transfer to my phone.
  - The phone has enough bandwidth (incl. write buffers, "disk" I/O,
    etc.) to sustain a 1gbps transfer from the server.

Or, I don't use WiFi (to a phone or otherwise) because if I *need*
1gpbs, then a wire's gonna give me that without any of the conditions
imposed by half-duplex radio communications.

>
>> It's not like an 802.11ax AP doesn't support a/b/g/n/ac ...
>
> You're missing the point, completely.

It's almost like the whole reason I've repeatedly asked "what do you
*REALLY* want to know" is because your question is vague.

  - If you're building some form of WiFi access point --> who cares,
    the phone will negotiate with the AP for the best common mode 
    between them given local conditions (e.g. 802.11n @ MCS2) 

  - If you're building some form of application that needs some minimum
    data rate --> you can't really guarantee you're going to get that 
    rate, unless it's less than 1Mbps (802.11a/b/g) or MCS0
    (802.11n/ac/ax; exact rate varies depending on available spatial
    streams).

-- 
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